This invention relates to a gas-insulated switchgear apparatus, especially, a phase-separated, double main bus type gas-insulated switchgear apparatus.
Typically, in gas-insulated switchgear apparatus of a double main bus type, gas-insulated circuit breakers are arranged horizontally and one end of each gas-insulated circuit breaker is connected to first and second sets of main buses in succession through breakers or disconnecting switches. Accordingly, the apparatus extends in the axial direction of the gas-insulated circuit breaker.
In conventional gas-insulated switchgear apparatus, main buses are used in a three-phase common busbar type or a phase-separated type. For example, three-phase common busbars are used in the gas-insulated switchgear apparatus in a way as disclosed in, for example, JP-A-56-62006, according to which gas-insulated circuit breakers for U, V and W phases are juxtaposed on a horizontal plane, each having one end connected to a coupling bus. First and second three-phase common main buses are arranged under the coupling buses to lie on a horizontal plane which is orthogonal to the horizontal plane, and a conductor for each phase of each of the first and second three-phase common main buses is connected to a conductor of the coupling bus for each phase through a disconnecting switch. Phase-separated main buses are typically used in the gas-insulated switch-gear apparatus as disclosed in JP-A-58-15410, which shows gas-insulated circuit breakers for three phases in the same horizontal plane, each having one end connected to a coupling bus. First phase-separated main buses are arranged above the coupling buses to lie on a first horizontal plane which is orthogonal to the coupling buses, second phase-separated main buses are arranged under the coupling buses to lie on a second horizontal plane which is orthogonal thereto, and the first and second phase-separated buses are connected to the gas-insulated circuit breakers through the coupling buses and disconnecting switches.
Because of the grouped three-phase main buses in previous switchgear apparatus, the overall apparatus size can advantageously be reduced. However, if a conductor of any phase becomes defective, it is difficult to inspect and repair this defective conductor without having some influence upon the conductors of the remaining phases. To eliminate this problem, the main buses for three phases can be separated as is the case with phase separation in the juxtaposed gas-insulated circuit breakers, but this means an increase in installation space.
However, when incorporating the upper set of first phase-separated main buses arranged above the installation horizontal plane for the gas-insulated circuit breakers and the lower set of second phase-separated main buses arranged below that installation horizontal plane into the gas-insulated switchgear apparatus, it is impossible to connect the conductors of the first and second phase-separated main buses to the coupling buses through the disconnecting switches by maintaining identiy of U, V and W phase sequence between the upper and lower sets. This is because of the limited arrangements available for the switches. As a result, an operator might erroneously recognize the phase of the main buses during maintenance inspection and repair. To solve this problem, the upper set of first phase-separated main buses and the lower set of second phase-separated main buses can be arranged in the same sequence of phases. This expedient, however, requires that the switches for connection or disconnection of the conductors be arranged in an artificially sophisticated fashion and that the distance between the horizontal plane for the upper or lower set of phase-separated main conductors and the installation horizontal plan for the gas-insulated circuit breakers be large, thus increasing the overall size, especially height, of the gas-insulated switchgear apparatus with a resultant degradation in vibration-proofing characteristics.
To cope with this problem, both the first and second phase-separated main buses may be juxtaposed under the installation horizontal plane for the gas-insulated circuit breakers. This arrangement however can not be realized without increasing the overall size in the direction where the phase-separated main buses are juxtaposed on the side of one end of each gas-insulated circuit breaker. This space must be large enough for drawing out or removing the gas-insulated circuit breakers and phase-separated main buses or the phase-separated main buses themselves and will increase the size of the gas-insulated switchgear apparatus, requiring a larger building for accommodating a larger-sized apparatus and a large ground area for foundation of the large building. In addition, since the phase-separated main buses are positioned differently, the length of the coupling bus connected to one end of the gas-insulated circuit breaker differs from phase to phase. Therefore, the individual coupling buses are not interchangeable and are unsuitable for mass production.